Abstract
A self-consistent rate equation model is presented to investigate the
influence of carrier relaxation on the modulation response of 1.3 $\mu$m InAs–GaAs quantum dot lasers. In this model, the
carrier dynamics in GaAs barrier, relaxation pathways, and the phonon- and
Auger-assisted relaxation are considered. The dependence of 3 dB bandwidth
on the relaxation time and relaxation pathway is discussed. It is shown that
carrier relaxation via less energy level has better
carrier confinement and higher 3 dB bandwidth. The improvement of bandwidth
by tunnelling injection QD structure is investigated from the point of view
of relaxation pathway. The different effects of tunnelling into ground state
and excited state on the 3 dB bandwidth are analyzed. The enhanced carrier
relaxation by p-type modulation doping and its effect on the bandwidth are
investigated. It is found that there exists a tradeoff on the improvement of
bandwidth by p-doping, which is explained as the competition between the
bandwidth limitation of $K$-factor and relaxation dynamics. Increase in the bandwidth of QD
lasers by improving both the carrier relaxation dynamics and $K$-factor limitation is discussed.
© 2009 IEEE
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